Furnaces



April 3, 1952 H. GREENHALGH 3,028,153

FURNACES Filed June 26, 1958 5 Sheets-Sheet 1 HAROLD C'rREE/YHALGH ,5y wL Arm/wey 5 Sheets-Sheet 2 FURNACES )A I l l I l l IIIIIIIII `.4.. l

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H. GREENHALGH April 3, 1962 Filed June 26, 1958 April 3, 1962 H. GREENHALGH 3,028,153

HAI/emo GnEE/YHALQH @y *Maly ATT/YEY April 3, 1962 H. GREENHALGH FURNACES 5 Sheets-Sheet 4 Filed June 26, 1958 FIGB.

FIGA.

INVENTOR HA ROL D GREENHA L GH Aff? April 3, 1962 H. GREENHALGH 3,028,153

FURNACES Filed June 26, 1958 5 Sheets-Sheet 5 F IG. 5.

INVENToR HA RoLD GREENHALGH Atty;

3,025,153 FURNACES Harold Greenhalgh,-Milford House, Milford, near Derby, England Filed June 26, 1958, Ser. No. 744,718 8 Claims. (Cl. 263-6) This invention has reference to furnaces of the continuous or tunnel type and is concernedy with mechanism for supporting workpieces within the tunnel or treatment chamber of a furnace whilst the said workpieces are undergoing treatment and/ or are being fed forwards through the tunnel. Whilst the invention is more particularly concerned with furnaces of the above type having electric induction units for heat treating workpieces such as metal billets, it is also applicable to furnaces having other forms of heating means, for example gas or like fuel red burners.

The principal object of the present invention is to prevent or minimise the internal surface of the tunnel being worn or otherwise damaged by the workpieces as the latter travel through the tunnel.

A further object of the invention is to ensure that, except when the workpieces are being fed through the furnace, they are located co-axially or substantially coaxially of the tunnel so as to minimise possible distortion due to uneven heating.

Other objects of the invention are to enable workpieces of different cross-sectional dimensions to be heated uniformly in any one furnace, and to simplify the construction, and minimise initial erection costs, of the furnace.

In order that the invention may be more readily understood and carried into practice, reference will now be made to the accompanying drawings wherein:

FIGURES 1, 1A and 1B show, partly in elevation and partly in section, an electric induction furnace, of the continuous or tunnel type, for heat treating metal billets, the billets being shown (in FIGURE 1A) seated upon their supports.

FIGURES 2, 2A and 2B are views, similar to FIG- URES 1, 1A and 1B respectively, showing (in FIGURES 2A and 2B) the billets raised from their supports.

FIGURE 3 is a section along the line a-a of FIGURE 2B, and FIGURE 4 is a section along the line b-b, FIGURE lA, certain parts having been omitted for the sake of clarity.

FIGURE 5 is an elevation, partly in section, of part of a tunnel furnace which is similar to that shown in FIG- URES 1-4 but is provided with diiferent work-raising mechanism, and

FIGURE 6 is a section along the line c-c, FIGURE 5.

Each of the two furnaces shown in the drawings comprises a treatment chamber or tunnel which is encased in a metal shell 1 and is built from a number of broad, coaxial units 2. Each unit includes a bored block-like body 3 of refractory cement, the bore of which extends from one side to the other of the said body and is lined with a refractory tube 4. Disposed within each body, around and in close proximity to the tube, is an electric induction coil 5 (indicated in broken lines) which is adapted to heat the billets 6 as the latter are fed through the tunnel, the heating within any one unit being uniform around the periphery of the billet provided that the latter is located concentrically of and within the tube.

Below the centre of the tube, each end of each body has a transverse recess formed therein so that when each two adjoining units are in end to end abutment, an aperture or opening 7 is formed in the underside, or floor, of the tunnel. Corresponding apertures are formed in the underside of the refractory lining and -register with the body apertures.

3,028,153 Patented Apr. 3, 1962 A work-support 8 is provided in and transversely of the leading end (that i's the end nearer the work discharging en'd of the furnace) of each two registering body and lining apertures, the said support comprising (see FIG- URE 4) two overlapping and superimposed refractory wedges 9, 10 arranged with their inclined edges in contact with one another. Any convenient means such as a manually rotatable shaft 1;'1, may be provided for adjusting the lower wedge 1l) transversely of the tunnel so that the distance by which the opposite and upper work-supporting edge of the wedge 9 is spaced from the tunnel floor, may be varied to suit the diameter of the billets undergoing treatment; hence, whatever' the said diameter may be (without reasonable limits), the wedge 10 may be so adjusted that when a billet isv being carried upon the wedge 9, the said billet may be positioned accurately in concentric relationship to the tunnel.

The length of the bored bodies is not greater than half the minimum length of any billets likely to be treated in the furnace; hence, the supports are so located that each and every one of the billets being treated in the furnace, seats upon and is supported by at least two of the supports when it is stationary within the tunnel. If desired, a separate block having a recessed work-supporting face may be carried upon and fixed to the upper wedge 9.

However, in-stead of consisting of two superimposed wedges as shown in FIGURE 4, each support may consist of two refractory wedges which are arranged sideby-side transversely of the corresponding tunnel opening, with their inclined and work-supporting edges uppermost and their deeper ends located laterally and on opposite sides of the tunnel so as to provide a central V-shaped supporting zone, both of the said wedges being adjustable to vary their degree of overlap and, consequently, the distance of the work-supporting portion of their upper edges from the tunnel floor.

The furnace shown in FIGURES 1 4 is provided with a number of lwork-lifting rollers 12 equal to the number of tunnel apertures 7, each roller being located vertically bel-ow a corresponding aperture with its axis extending transversely of the tunnel. Each roller is carried by yan axle 13 which is journalled in and between two brackets 14 fixed to and projecting upwardly from a beam structure 15. The said beam structure is disposed below and lengthwise of the tunnel and the brackets are carried upon laterally extending platforms 16, 17 provided on opposite sides and at intervals apart lengthwise of the beam structure. Chain driven sprocket wheels 18 are made fast upon the roller-axles so that all the rollers are adapted to be rotated simultaneously and at the same speed; alternatively, the roller axles may be gear driven or may be allowed to run freely so that they are adapted for rotation solely by forwards travel `of the work through the furnace.

Since each roller is located vertically below a corresponding one of the body apertures, it is adapted to be rai-sed into, through and beyond the aperture into the interior of the tunnel to an upper extreme position wherein its periphery projects above the level of the worksupporting edges of the refractory supports thereby raising the billets from and clear of the supports, and then lowered to an alternative and lower extreme position which preferably is `located below the underside of the tunnel, thereby enabling the billets to reseat upon the supports; whilst the rollers are in their upper extreme positions, the billets are fed forwards through the tunnel in end-to-end abutment either by a known feed device 19 and/or by the rotation of the rollers. When seated upon the supports, the billets are disposed concentrically of the tunnel so that they may be heated uniformly thereby minimising any tendency for the for the billets to lbow or otherwise distort.

To permit simultaneous lifting and lowering of the brackets and rollers, the beam structure is carried by a number of arms 20 which are pivoted upon the said structure at intervals along its length. Each arm is pivoted at its mid-point and extends upwardly and downwardly of its pivot, its opposite ends being connected respectively to an upper lever 21 and a lower lever 22 pivoted upon the fixed framework 23 of the furnace equidistantly from and on opposite sides of the arm; certain of the lower levers 22a are of the bell crank type and are coupled to a reciprocable rod 24 extending lengthwise of the furnace below the said bell crank levers 22a. The arrangement is such that upon imparting endwise movement to the rod towards the charging end of the furnace, the bell crank levers 22a are turned and lift the pivoted arms together with the beam structure, the brackets and rollers, the a-rm pivots being constrained to move in vertical paths as a consequence of their connection to the upper and lower levers. A reverse movement of the rod returns the beam structure to its initial position. The rod is reciprocable by a connecting rod 25 carried by a motor driven crank 26 located below a charging table 27.

The feed device 19 is timed to transfer a billet 6 from the table 27 into the tunnel as the rollers reach the upper extreme position and have raised the billets already in the tunnel from their supports so that a forward step is imparted to the said billets by the insertion of a fresh billet through the charging end of the furnace and by the rotation of the rollers.

If desired, shutters may be provided `for closing the tunnel apertures, the said shutters being adapted for actuation in a manner which ensures that they are moved to their aperture-'opening positions as the rollers enter the apertures and are returned to their aperture-closing positions as the rollers emerge from the outer ends of the apertures.

The induction coils in the tunnel units may be rated so as to divide the tunnel interior into three separate but contiguous heating zones, namely, a preheating zone at the charging end of the furnace in which the billets are heated gradual-ly, a central treatment zone in which the billets are raised rapidly to treatment temperature, and a soaking Zone at the discharging end of the furnace in which the heat supplied is sufficient only to compensate for heat losses and the billets are maintained at or somewhat below treatment temperature.

In the furnace shown in FIGURES and 6, the billets are adapted to be fed through the tunnel in a more or less continuous manner, and for this purpose the beamsupported rollers are replaced by refractory blocks 28 each of which is disposed in and transversely of the corresponding tunnel aperture in spaced relationship to the support 8 in the same aperture. From an initial position wherein the blocks are located in the ends of their respective apertures adjacent the charging end of the furnace and below the work-supporting edges of the supports, the said blocks are adapted to be raised rst into lifting contact with the billets, moved towards the supports, lowered away from the billets, and then returned to their initial positions, the said sequence of movements being repeated continuously.

The mechanism for imparting the said sequence of Y movements to all the blocks simultaneously, comprises an overhead longitudinally reciprocable and multi-section rod 29 which extends along the length of one side of the furnace and is operatively connected to the adjacent end of each refractory block through one arm of a corresponding bell crank lever 30 pivoted by its elbow to a bracket 31 fixed upon a beam 32 incorporated in the framework of the furnace, and a depending link 33, of which the upper end is pivoted to the other arm of the bell crank lever and its .lower end is coupled to the end ter is inserted into the charging end of the furnace.

of the block. A second multi-section rod 34 extending lengthwise of the furnace is pivotally connected to all the depending links between the ends of the latter. The bell crank lever adjacent one end of the furnace is formed with an ear 35 Awhich is pivotally connected to one end of an operating rod 36 of which the opposite end is journalled upon a pin 37 projecting from and eccentrically of a gear wheel 38; similarly the corresponding end link 33 is formed, between its ends, with an ear 39 which is pivotally connected to one end of an operating rod 40 of which the opposite end is journalled upon a pin 41 projecting from and eccentrically of a second gear wheel 42. The two gear wheels are disposed upon opposite sides of and are in constant mesh with an intermediate gear wheel 43 which is fast upon one end of a motor driven shaft 44 extending across and above the furnace. A second and identical intermediate gear wheel fast upon the opposite end of the driven shaft 44, is in constant mesh with gear wheels which are identical to the wheels 38 and 42 respectively and are operatively coupled to the other ends of the blocks 28 through a rod, lever and link system which is identical to that described and is indicated in FIGURE 6.

The rotation of the gear wheels 38 reciprocates the rods 36 and 29 to oscillate the bell crank levers in unison, thereby lifting and lowering the links and the refractory blocks. rIhe rotation of the gear wheels 42 also reciprocate the rods 40 and 34 to swing the links backwards and forwards about their pivotal connections to the bell crank levers, thereby reciprocating the said blocks within their respective tunnel apertures, the wheels 3S and 42 being set in such relative relationship that in each cycle of operations, the bell crank levers are swung towards the gearing to lift the links and the blocks so as to raise the billets from the supports, the links are swung towards the said gearing to carry the blocks and the billets towards the work-discharging end of the tunnel, the bell crank levers are swung in the reverse direction tto lower the blocks and re-seat the work on the upports, and the links are swung in the reverse direction to return the blocks to their initial positions without moving the billets. Therefore, by rotating the motor `driven shaft continuously, the billets are fed through the tunnel intermittently in a succession of equal steps, the blocks functioning as a type of walking beam.

Hence, in both cf the furnaces shown in the drawing, the billets are out of contact with their supports during the whole of each forwards feeding movement so that wear on the said supports is reduced to a minimum. In the furnace shown in FIGURES 1-4, the billets are fed through the tunnel in steps or stages by, and through distances equal to the length of, each fresh billet as the lat- In the furnace shown in FIGURES 5 and 6 the billets are fed forwardly through steps or stages equal to the distance between the rod-actuated block and the work-support accommodated within the same tunnel aperture and, during each step or stage are supported upon and moved by the said blocks so that, again, wear on the supports is reduced to a minimum.

To avoid the possibility of the same portion of a billet being disposed above two registering body and lining apertures every time it is lowered onto the supports for further heat treatment as might happen when the billets are of a length equal to a multiple of the pitch of the roller axes, means are provided in the furnace shown in FIG- URES l-4, whereby the leading billet may be halted at either one or two alternative positions at the discharge end of the furnace immediately before discharge. For example, two limit switches (not shown) may be so installed at the discharge end of the furnace that they are spaced apart lengthwise of the tunnel by a distance which is a fraction of the length of the individual billets; each of the said switches may comprise a finger 45 which projects into the interior of the tunnel so that it is located in the path of travel of the leading billet and is actuated by the impact of the said billet to open the corresponding switch for temporarily halting the forward travel of the leading billet and, therefore, all the other billets undergoing treatment and to be withdrawn clear of the said work piece at the commencement of the next discharge operation; hence, by arranging for the two fingers to be projected into the tunnel alternately, alternate leading work pieces are halted in different positions relatively to the body and lining apertures between successive discharge operations.

Whilst the said description and drawing describes and illustrates a typical embodiment of the invention, it is to be understood that departures may be made therefrom Within the scope of the invention which is not to be limited to the details disclosed herein, but is to be accorded the full scope of the claims so as to embrace any and all equivalent furnaces.

What I claim is:

1. A tunnel type furnace for the continuous treating of elongate articles, comprising a framework defining a tunnel having a oor, contiguous refractory Work supports carried transversely of the tunnel at intervals along the length of the tunnel floor, upper wor-k supporting edges of the work support being spaced from said floor, apertures through the tunnel floor transversely thereof adjacent said supports, work-raising mechanism mounted on the tunnel framework longitudinally of the furnace, work-raising members corresponding to each of said apertures, said work raising members being reciprocable in said apertures in response to the work raising mechanism, said work raising mechanism being adapted to raise the work-raising members above said upper work supporting edges, and means for advancing the work along the tunnel while the work is lifted from the work supports by the work raising members.

2. A tunnel type furnace as claimed in claim 1 wherein each of said supports comprise a refractory wedge carried on the tunnel floor adjacent each of said apertures, an upper work supporting edge being provided on said wedge, a further refractory wedge overlapping said wedge and means for moving one of said wedges transversely of the tunnel to vary the distance by which said work supporting edge is spaced from said floor.

3. A tunnel type furnace as claimed in claim 1 wherein the work-raising mechanism comprises a rod extending longitudinally of the furnace, bell crank levers pivotally carried on the tunnel framework and pivotally connected to the rod, a further member associated with the workraising members and extending longitudinally of the furnace, said further member being pivotally connected to each of said bell crank levers.

4. A type furnace comprising a tunnel framework defining a tunnel having a oor, contiguous refractory work supports carried transversely of the tunnel at intervals along the length of the tunnel oor, upper Worksupporting edges of the work supports being spaced from said floor, apertures through the tunnel floor transversely thereof adjacent said supports, a carrier extending longitudinally of the furnace, rollers corresponding to said apertures and extending transversely of the tunnel door, each roller being mounted on the carrier, and raising mechanism for reciprocating the carrier and raising the rollers in said apertures above said upper work supporting edges.

5. A tunnel type furnace comprising a framework defining a tunnel having a floor, refractory work supports provided at intervals along the length of the floor, upper work supporting edges of the work supports being spaced from the tunnel floor, transverse apertures through the tunnel floor at intervals along the length thereof, refractory blocks carried in said apertures and extending transversely of the tunnel iioor, work-raising mechanism for reciprocating said blocks in said apertures into a raised position above said work supporting edges, feeding means for reciprocating said blocks longitudinally of the tunnel in said apertures and advancing said blocks when in said raised position.

6. A tunnel type furnace as claimed in claim l wherein said working raising mechanism is adapted to lower said work raising members from said apertures.

7. A tunnel type furnace as claimed in claim 4, wherein the work raising `mechanism comprises arms pivoted intermediate their ends to said carrier at intervals along the latter, upper ends and lower ends of the arms, upper levers pivoted to said upper ends of the arms and to said tunnel framework, and bell crank levers pivoted intermediate their ends to said tunnel framework, the ends of the bell crank levers being pivoted respectively to said lower ends of the arms and to a longitudinally reciprocable rod extending lengthwise of the furnace.

8. A tunnel type furnace as claimed in claim 5 wherein the work raising mechanism comprises links pivoted to said blocks, bell crank levers pivoted intermediate their ends to said tunnel framework, ends of the bell crank levers, said ends being pivoted respectively to said links and to a first longitudinally reciprocable rod extending lengthwise of the furnace and said feeding means comprising a second longitudinally reciprocable rod extending lengthwise of the furnace, said second rod being pivotally connected to each of said links.

References Cited in the file of this patent UNITED STATES PATENTS 1,205,690 Wetcke Nov. 21, 1916 1,761,199 Drake June 3, 1930 2,014,302 Waldron Sept. 10, 1935 2,859,023 Bucci Nov. 4, 1958 2,875,995 Troglione Mar. 3, 1959 FOREIGN PATENTS 493,184 Great Britain Oct. 4, 1938 

